Transom drive for motorboats



April 4, 1944. A w. J. SNADECKI, 2,345,689,

TRANSOM DRIVE FOR MOTOR BOATS Filed Nov. 18, 1942 Patented Apr. 4, 1944 UNITED STATES PATENT OFFICE TRANSOM DRIVE FOR MOTORBO A'ITS William J. Snadecki, Newprt News, Va. Application November 18, 1942, Serial No. 466,072 3 Claims. (01. 115-41) My invention relates to motor boat drives of the type commonly known as transom drives, in which the power is transmitted from a motor installed aft in the boat, by means of a shaft from the motor extending through the transom stern and a suitably connected transmission shaft operating through suitable connections to drive the propeller shaft.

Various modifications of this general type include those in which the drive unit is rigidly mounted on the stern transom, and the transmission shaft is connected to the propeller shaft directly by means of a c-ountershaft and gearing, or by means of sprockets on transmission shaft and propeller shaft and chain connection,

the boat being steered by means of a rudder mounted abaft the propeller, the rudder post intersecting the extended axis of the propeller shaft, and extending above and below this axis. In such a construction, a rudder of relatively large area is required for efiicient service as it operates in the swirl or back wash of the propeller, and the stream action is of a character that detracts from sensitive rudder action.

With drives of this character, there is generally a fin downwardly extending from the housing surrounding the drive mechanism, adapted to protect the propeller by engaging any underwater obstruction which would otherwise damage the propeller. In my invention I do not depend alone upon this fin as a protecting means, but provide means operative to permit the whole drive unit to swing backwardly should the unit or propeller meet an obstruction in the forward movement of the boat, and at the same time stop the operation of the unit.

One object of my invention is to provide means for disconnecting the operation of the drive unit in case the propeller or contiguous housing should meet obstruction in the forward move-- ment of the boat.

A second object is to provide a transom drive in which the current flowing from the propeller assures a more even stream action on the rudder.

A further object is to provide a transom drive with a more efficient rudder action with a smaller area of rudder surface.

My invention consists in the novel construction of the drive unit, the means employed for safe guarding the mechanism thereof, and the arrangement and construction of the rudder.

I have found that by using a chain drive from the transmission shaft to the propeller shaft,

spreading the lines of chain, and providing an opening betweemthrough the housing, that I am enabled to provide a relatively free and uniform stream from the propeller to the rudder mounted abaft the housing. This stream operates on the rudder with superior efiiciency, to keep the boat moving in a straight line, and facilitating maneuvering when making a sharp turn.

As the stream is uniform, a rudder of less area is required to perform the service-which one of greater area has to perform in a swirling backwash. r

In the accompanying'specification and claims. and the drawing forming a part thereof, I have described and illustrated a preferred form of my invention, but do not confine myself to the embodiment shown, as modifications may be made within the scope of the appended claims.

. In the drawing,

Fig. 1 is a sectional side elevation of this preferred embodiment, substantially on the line l-|, Fig. 2. i

Fig. 2 is'a sectional rear elevation, substantially on the line 2-2, Fig. 1.

Fig. 3 is a sectional plan substantially on the line 3-3, Fig. 2.

Fig. 4 illustrates the operation of the drive unit after passing over anunderwater obstruction.

Referring to the drawing,

The motor boat A is provided with a transom drive unit including the propeller l2, rigid with the shaft l3.

This shaft is driven from the transmission shaft H, by means of the sprockets [4, I5 and the chain IS. A housing about the sprockets and chain includes the two parts I8, and I9 assembled, the transmission shaft I1 projecting therefrom and being connected with the shaft 20 of a motor not shown, installed in the boat, the housing being hinged at It] to the transom stern, and secured below as will be hereinafter explained. Rotatably-mounted in the housing at 2|, are the idlers 22, operating to spread the lines of chainC, D, connecting the sprockets l4 and I5. Conduits 23, forming a part of the housing element l9, connect the lower portion of this element with the interior of the housing element l8. This portion 24 of the housing, is stream lined, and the contiguous walls of the conduits, 23, bound an open area B, through which the stream from the propeller l2 flows in a uniform current. Suitable thrust bearings 25, 26 are provided for the shaft l3 to which the propeller is rigidly secured. The rudder 35! is hung abaft the housing and operates directly in the stream flowing through the opening B, and entirely above the extended axis of the shaft I3, thus avoiding all swirl from below or on the sides of the housing.

The rudder post 3| is journaled in suitable bearings integral with the housing as at 32, 33, and is operated by any suitable means, here shown as the tiller 34. A fin 35, downwardly extending from the housing portion 24, operates to protect the propeller from damage in case an underwater obstruction is encountered which might damage the propeller.

As there is necessarily a backlash inthe chain, I provide means for automatically tightening the chain when the motor is operating either forward or in reverse, and the following is a preferred means to this end;

Idlers 40, 4|, are rotatably mountedon levers 42, 43, which are journaledpreferably on the shafts of the sprockets at 2!, but may be mounted in any suitable position relative to respective lines of the chain. These idlers bear on the outsides of respective chain lines, and the levers 42, 43 are connected under a yielding tension, here shown as the spring 44.

As the rotation of the transmission shaft operates to tighten the line of chain C, the action of the spring is such that the idler 4| takes up the slack formed in the chain line D.

When the motor is reversed, the line D is drawn taut, and the slack in chain line C is taken up in a similar way, the yielding tension between the levers being constant, and the levers being journaled to compensate for slight swing of the levers due to the slack changing from one chain line to the other.

Referring to the mounting of the drive unit on the boat.

The housing, hinged as explained at 10 to the 1 stern transom II, is releasably secured near the bottom end of element H! in the following preferred manner.

Rigid with the stern transom near the bottom of the boat are clevises 55, and projecting from the housing element l9 are corresponding clevises 56. Links 51 arejournaled at B in the clevises 55, the opposite ends of the links engaging the clevises 56 on the housing element l9, and connected thereto by shear pins 59, adapted to shear and permit the entire housing to swing in case an underwater obstruction is encountered. The transmission shaft H engages with the motor shaft 20, under normal conditions, by suitable means adapted to be disengaged. I have shown one means in the clutch members 52, 53 secured to respective shafts, but any means by which the two shafts may be disengaged, will serve the same purpose.

Should the propeller or fin strike an underwater obstruction while the boat is moving forward, the unusual strain will operate to shear the pins 59, permitting the whole unit to swing backward and upward on its hinges 10, the links rotating on their journals 58,, and dropping to a vertical position, at the same time the clutch members disengage, and the rotation of the propeller is stopped. As the obstruction is passed, the unit tends to swing back to normal position but projections from the housing element l9 engage the links 51, preventing return of the unit to normal position and the engagement of the clutch members 52, 53, until such time as the links are readjusted to secure the unit in operative position.

Having thus described my invention, I claim:

1. In a transom drive for motor boats, having a fixed motor within the boat, a drive shaft connected therewith and extending through the transom of the boat, a housed unit hinged to the transom, and in which are mounted a propeller shaft, a transmission shaft and operative driving mechanism connecting said shafts, separable connections between the motor driven shaft and the transmission shaft, in combination therewith, means for securing the housing in operative relation to the motor driven shaft, including links swivelled to the transom and having their opposite ends connected to the housing by elements adapted to release under undue strain acting in the direction of the axis of the boat, permitting the links to swing downwardly, projections from the housing adapted to engage the links in their released position as the housing swings toward normal, the engagement with the links operating to prevent reengagement of the transmission and motor driven shaft.

2 In a transom drive for motor boats of the character described in claim 1, and in which the operative connection between the transmission and propeller shafts include a sprocket rigid with each shaft, and chain connection therebetween, in combination therewith, means for taking up the slack of the chain including a pair of idlers, rotatably mounted to bear on respective lines of chain, and movable towards and from respective lines: yielding connection between the mountings operating to exert a yielding, uniform tension of the idlers on respective lines of chain in either forward or reverse action of the a motor.

3. In a transom drive for motor boats of the character described in claim 1, and in which the operative connection between the transmission and propeller shafts include a sprocket rigid with each shaft, and chain connection therebetween, in combination therewith, meansfor taking up the slack in the chain, including a pair of levers journaled in the housing on opposite sides of a line through the axes of the transmission and propeller shafts, idlers rotatably mounted on the opposite ends of respective levers, and adapted to bear on the outsides of respective lines of chain between the sprockets; and means connecting the levers to exert a yielding uniform pressure on the levers to press the peripheries of the idlers against the respective lines of chain in either forward or reverse action of the motor.

WILLIAM J. SNADECKI. 

